imghash-bbassi/index.js

Image perceptual hash calculation for node. Based on package imghash v0.0.7 but fixes that is waiting to go upstream.

"use strict";

const fs = require("fs");
const blockhash = require("blockhash-core");
const { imageFromBuffer, getImageData } = require("@canvas/image");
const imageType = require('image-type')
const jpeg = require('jpeg-js');
const { resolve } = require("path");

function hash(filepath, bits, format) {
  format = format || "hex";
  if (format !== "hex" && format !== "binary")
    throw new Error("Unsupported format");

  bits = bits || 8;
  if (bits % 4 !== 0) throw new Error("Invalid bitlength");

  return new Promise((resolve, reject) => {
    if (Buffer.isBuffer(filepath)) {
      return resolve(filepath);
    }

    fs.readFile(filepath, (err, content) => {
      if (err) return reject(err);
      resolve(content);
    });
  })
  .then((fdata) => {
    return imageFromBuffer(fdata)
    .then((image) => {
      return getImageData(image);
    })
    .catch((err) => {
      const ftype = imageType(fdata);
      if (ftype.mime === 'image/jpeg') {
        return jpeg.decode(fdata, {maxMemoryUsageInMB : 1024});
      } else {
        throw err;
      }
    })
  })
  .then((data) => hashRaw(data, bits))
  .then((hexHash) => {
    if (format === "hex") return hexHash;
    if (format === "binary") return hexToBinary(hexHash);
  });
}

function hashRaw(data, bits) {
  return blockhash.bmvbhash(data, bits);
}

function hexToBinary(s) {
  const lookup = {
    "0": "0000",
    "1": "0001",
    "2": "0010",
    "3": "0011",
    "4": "0100",
    "5": "0101",
    "6": "0110",
    "7": "0111",
    "8": "1000",
    "9": "1001",
    a: "1010",
    b: "1011",
    c: "1100",
    d: "1101",
    e: "1110",
    f: "1111",
    A: "1010",
    B: "1011",
    C: "1100",
    D: "1101",
    E: "1110",
    F: "1111",
  };
  let ret = "";
  for (let i = 0; i < s.length; i++) {
    ret += lookup[s[i]];
  }
  return ret;
}

function binaryToHex(s) {
  const lookup = {
    "0000": "0",
    "0001": "1",
    "0010": "2",
    "0011": "3",
    "0100": "4",
    "0101": "5",
    "0110": "6",
    "0111": "7",
    "1000": "8",
    "1001": "9",
    "1010": "a",
    "1011": "b",
    "1100": "c",
    "1101": "d",
    "1110": "e",
    "1111": "f",
  };
  let ret = "";
  for (let i = 0; i < s.length; i += 4) {
    let chunk = s.slice(i, i + 4);
    ret += lookup[chunk];
  }
  return ret;
}

module.exports = {
  hash,
  hashRaw,
  hexToBinary,
  binaryToHex,
};